Aromatic compounds include pollutants, carcinogens, and disinfectants. Many bacteria, including some pathogens, can grow on various of these compounds. Aromatics can diffuse through cell membranes and for this reason bacteria have been thought not to have specific mechanisms to recognize the presence of aromatics in the extracellular medium. Recently, however, aromatics have been shown to be chemoattractants for some bacteria and Pseudomonas has been found to synthesize inducible chemoreceptors for benzoate and a number of other aromatic acids. The proposed research will explore the mechanism and molecular basis of benzoate chemoreception. The benzoate chemoreceptor gene region from Pseudomonas putida will be cloned and its molecular organization examined. The number and sizes of gene products specified by the benzoate chemoreceptor operon will be analyzed and site-directed mutagenesis will be used to define and characterize the regulatory region of the operon. Physiological approaches will complement molecular approaches and be used to examine the subcellular location of the benzoate chemoreceptor and determine how sensory information that is received by the chemoreceptor flows to the rest of the cellular chemotaxis machinery. Because benzoate is lipophilic and has an aromatic structure, the benzoate chemoreceptor quite probably has structural characteristics that are very different from those of the well-studied chemoreceptors of other bacterial systems and it is also possible that the benzoate chemoreceptor has a unique intracellular location. Thus these studies should provide new information about bacterial sensory behavior in general. These studies will also be expected to increase our understanding of initial interactions that occur when bacteria encounter aromatic acids in the environment and they will augment the relatively small bank of knowledge that presently exists about the genetic organization of pseudomonads.